The photoelectrical elements include many types such as the light-emitting diode (LED), the solar cell, and the photo diode. Take the LED as an example, the LED is a kind of the solid state semiconductor device, which at least comprises a p-n junction formed between the p-type and the n-type semiconductor layers. When a bias is applied to the p-n junction, the holes of the p-type semiconductor layer combine with the electrons of the n-type semiconductor layer to emit the light. The region where the light is emitted from is called the light-emitting region.
Now, the LED generally has the problem, which is the current spreading not well. In the case of the LED with a top p-type semiconductor, a p-type semiconductor is formed on the light emitting layer and an electrode pad is formed on the p-type semiconductor to lead in the current. The mostly used method to improve the current spreading is that: a current spreading layer such as the metal oxides or GaAs is formed on the p-type semiconductor layer, and an electrode pad is formed on the current spreading layer. Further, one or a plurality of extension electrodes is extended from the electrode pad to improve the current spreading. Even the structure described above is used to improve the current spreading for the LED, the problem of the current crowded still exists in the electrode pad or under the extension electrode thereof.
Otherwise, the LED also has the heat dissipation problem. When the temperature of the light emitting layer is over high, the recombination rate of the electrons and the holes decreases and the luminous efficiency is impacted. The above-described LED further connects with the other elements to form the light-emitting apparatus. The above-described light-emitting apparatus comprises a sub-mount comprising at least one electric circuit; at least one solder formed on the above-described sun-mount, whereby binding the above-described LED to the sub-mount and electrically connecting the substrate of the LED and the electric circuit of the sub-mount; and an electrical connection structure electrically connecting the electrode pad of the LED and the electric circuit of the sub-mount, wherein the above-described sub-mount comprises the lead frame or the large-scaled mounting substrate, so as to design the electric circuit of the light emitting apparatus and raise the heat dissipation.